Stable, anticorrosive peracetic/peroxide sterilant

ABSTRACT

PCT No. PCT/US92/05877 Sec. 371 Date Dec. 9, 1993 Sec. 102(e) Date Dec. 9, 1993 PCT Filed Jul. 14, 1992 PCT Pub. No. WO93/01822 PCT Pub. Date Feb. 4, 1993.Stable microbicides comprising hydrogen peroxide, peracetic acid, acetic acid and purified water substantially free of contaminants, sequestrants or stabilizers and having anticorrosive properties for metals used in surgical and dental instruments is disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of microbicides. Inparticular, it relates to a stable microbicide having anticorrosiveproperties comprising a mixture of hydrogen peroxide, peracetic acid,acetic acid and purified water which is substantially free ofcontaminants or stabilizing and sequestrant type additives.

2. Description of the Related Art

Peracetic acid/peroxide containing compositions have a long history ofuse as disinfectants and sterilizers due to their microbicidalactivities. However, peroxide containing compositions arehigh-energy-state compounds and as such can be consideredthermodynamically unstable. Therefore, because there is a strongtendency for these compositions to decompose in the presence ofmultivalent metal ions, stabilizers are added. Stabilizers may be agentssuch as sodium pyrophosphate, phosphonic acid or chelating agents suchas 8-hydroxyquinoline. Stabilizers act by removing trace metals whichaccelerate the decomposition of peroxides. Stabilizers also acceleratethe reaction between hydrogen peroxide and acetic acid to form peraceticacid. Therefore, for any given concentration of hydrogen proxide andacetic acid, the addition of a stabilizer increases the concentration atequilibrium of peracetic acid.

While conventional art compositions are stable due to the use of addedstabilizers, they are also highly corrosive to the very metals they aredesigned to disinfect namely surgical and dental instruments made ofaluminum or brass, which instruments are often plated with an ornamentalor protective layer of nickel or nickel and/or chromium. Additionally,certain susceptible individuals often exhibit allergic reactions to theconventional art formulations. Further, after prolonged use theseconventional art formulations often leave mineral-like deposits on themetal instruments they sterilize.

A concentrated composition that contains no stabilizer or sequestranttype additives that is both stable during storage for prolonged periodsof time and possesses anticorrosive properties would be a decidedadvantage over these conventional formulations. Further, a use-dilutionformulation that may be reused several times, is stable for relativelylong periods in the diluted form and possesses anticorrosive propertieswould be a further advantage over conventional formulations.

SUMMARY OF THE INVENTION

It is an object of the stable, anticorrosive concentrate anduse-dilution microbicides in accordance with the present invention tosolve the problems outlined above that has heretofore inhibitedlong-term storage and the anticorrosive sterilization of surgical anddental instruments. These improved microbicide solutions not only havethe desired stability but have been shown to have a significantlyreduced corrosive effect on certain metals than those of conventionalart mixtures of the peracetic acid/peroxide types known to theapplicants.

In accomplishing the foregoing objectives, there has been provided inaccordance with the present invention a stable, anticorrosive tosurgical and dental metals concentrate including peracetic acid, aceticacid, hydrogen peroxide and purified water mixed in a ratio of fromabout one to eleven parts total acid to one part hydrogen peroxide. Thenew concentrate has from substantially about 0.001 ppm to 200 pm, morepreferably from about 0.001 ppm to 100 ppm, and most preferably fromabout 0.001 ppm to 10 ppm of added stabilizers, such as phosphonicacids, sodium pyrophosphates and from about 0.001-10 ppm of ionic andnon-ionic contaminants such as divalent and trivalent ions, with noadded surfactants, such as ethoxylated decyl alcohols, sulfonate andsulfate types.

In accordance with another aspect of the present invention, there hasbeen provided a stable, anticorrosive to surgical and dental metalsuse-dilution formulation including a concentrate consisting essentiallyof at equilibrium peracetic acid, acetic acid, hydrogen peroxide and anaqueous diluent, said concentrate characterized in having from about0.001-200 ppm of added stabilizers, from about 0.001-10 ppm of ionic andnonionic contaminants and no added surfactants; and a purified aqueousdiluent; wherein the concentrate is diluted in the aqueous diluent fromabout 20 to 40 times.

In accordance with still another aspect of the present invention, therehas been provided a process for preparing a sterilant concentrate asdescribed above, including the steps of introducing from about 17% byweight to about 40% by weight hydrogen peroxide into a mixing drum, thehydrogen peroxide having from about 0.001-200 ppm of added stabilizers;blending thereinto from about 10% by weight to about 16% by weightacetic acid; and adding a purified aqueous diluent having from about0.001-10 ppm of divalent and trivalent ions; wherein the equilibriumconcentration includes from about 16-38% by weight hydrogen peroxide;from about 2.5-9% by weight acetic acid; from about 1.5-6.0% by weightperacetic acid; and an aqueous diluent and wherein the equilibriumconcentration is characterized in having from about 0.001-200 ppm ofadded stabilizers, from about 0.001-10 ppm of ionic and nonioniccontaminants and no added surfactants.

One of the advantages of the present invention is that the occasionalallergic reactions of some individuals to the conventional artformulations is reduced. Another advantage of the present invention isthat the presence of mineral-like deposits from the use of the solutionsof conventional art formulations containing sequestrants or stabilizersis no longer found. Perhaps most importantly, however, the presentinvention allows metal instruments such as dental tools and surgicalinstruments to be sterilized with significantly reduced corrosivity aswill be shown.

Further objects, features and advantages of the present invention willbecome apparent from the detailed description of the preferredembodiments, including the best mode, which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 4.1% by weight of peraceticacid and the storage temperature was at ambient temperature of 22° C.;

FIG. 2 is a chart of stability of concentrated microbicide where theinitial formulation contained 4.5% by weight of peracetic acid and thestorage temperature was 35° C.;

FIG. 3 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 4.2% by weight of peraceticacid and the storage temperature was 50° C.;

FIG. 4 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 23% by weight of hydrogenperoxide and the storage temperature was 22° C.;

FIG. 5 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 23% by weight of hydrogenperoxide and the storage temperature was 35° C.;

FIG. 6 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 23% by weight of hydrogenperoxide and the storage temperature was 50° C.;

FIG. 7 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 23% by weight of hydrogenperoxide, 4% by weight of peracetic acid and 8.4% acetic acid and thesolution was stored at ambient temperature;

FIG. 8 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 23.8% by weight hydrogenperoxide and 4.47% by weight peracetic acid and the solution was storedat ambient temperature;

FIG. 9 is a chart of stability of the concentrated microbicide againsttime where the initial formulation contained 23.8% by weight hydrogenperoxide and 4.47% peracetic acid and the storage temperature was 35°C.;

FIG. 10 is a chart of stability of the concentrated microbicide wherethe initial formulation contained 23.8% by weight hydrogen peroxide and4.47% by weight peracetic acid and the storage temperature was 50° C.;

FIG. 11 is a chart of stability of the concentrated microbicide wherethe initial formulation contained 17.2% by weight hydrogen peroxide and0.0% by weight peracetic acid and the solution was stored at ambienttemperature;

FIG. 12 is a chart of stability of the concentrated microbicide wherethe initial formulation contained 36.46% by weight hydrogen peroxide and0.0% by weight peracetic acid and the solution was stored at ambienttemperature;

FIG. 13 is a chart of stability of the concentrated microbicide wherethe initial formulation contained 27.4% by weight hydrogen peroxide and5.6% by weight peracetic acid and the solution was stored at ambienttemperature;

FIG. 14 is a chart of stability of the concentrated microbicide wherethe initial formulation contained 27.4% by weight hydrogen peroxide and5.3% by weight peracetic acid and the solution was stored at 50° C.

DETAILED DESCRIPTION OF THE INVENTION

Concentrate microbicide formulations in accordance with the presentinvention possess the desirable property of a long storage life withoutdeleterious decomposition despite the absence of conventional additionsof stabilizers and sequestrants as heretofore taught in the art.Additionally, the concentrate compositions of the present invention arefar less corrosive to metals that are sterilized using the compositionssuch as surgical and dental instruments. In contrast with conventionalart formulations containing added surfactants, sequestrants and otherstabilizers where visible evidence of corrosion of the metals appearedin one or two hours, formulations in accordance with the preferredembodiment of the present invention visibly showed comparatively littlecorrosion on the same metals during the same time period.

Manufacture of the preferred embodiment is effected by mixing a solutionof hydrogen peroxide with acetic acid diluted with a purified aqueousdiluent. The hydrogen peroxide is selected from commercially availablesources having low concentrations of stabilizers, preferably 0.001 ppmto 200 ppm, more preferably from about 0.001 ppm to 100 ppm, and mostpreferably from about 0.001 ppm to 15 ppm of added stabilizers, such asphosphonic acids, sodium pyrophosphates. Sources of such hydrogenperoxide are available from FMC Corporation (Philadelphia, Pa.).

In addition, the preferred embodiment in accordance with the presentinvention preferably includes no contaminants. Contaminants such asdivalent and trivalent ions, principally, iron, manganese, magnesium,nickel and cobalt, and undesirable trace organics found in themanufacturing process, principally, surfactants, acetone, methanol,ethanol, which are typically present in conventional art formulationsare found in the present invention in amounts preferably from about 5-10ppm and most preferably from about 0.001-5 ppm in the final composition.

Referring to Table I, the preferred composition is shown.

                  TABLE I                                                         ______________________________________                                               Initial Mixture                                                                              After Equilibrium                                       ______________________________________                                        H.sub.2 O.sub.2                                                                        17-40% by wt.    16-38%   by wt.                                     HOAc     10-16% by wt.    2.5-9.0% by wt.                                     HOOAc    0                1.5-6.0% by wt.                                     ______________________________________                                    

The concentrate microbicide in accordance with the present invention maybe formulated over a wide range of concentrations of the activematerials. After equilibrium the concentrate microbicide may have ashigh as 38% by weight hydrogen peroxide at equilibrium with theperacetic acid concentration ranging from 1.5% to 6.0% as indicated inTable 1. Since the concentrate when initially mixed contains noperacetic acid and therefore is not used immediately, it is stored forapproximately 19-20 days until the solution equilibrates and peraceticacid is formed by the reaction of hydrogen peroxide with acetic acid asillustrated in Reaction 1.

REACTION 1

    CH.sub.3 CO.sub.2 H+H.sub.2 O.sub.2 →CH.sub.3 CO.sub.3 H+H.sub.2 O

The concentrate manufactured in accordance with the present invention isstored and shipped in amber colored plastic bottles that have beenthoroughly precleaned with purified water to ensure no heavy metalcontamination. Stability studies were run at ambient (22° C.), 35° C.and 50° C. to determine the stability of the concentrate over time atthese temperatures. Data regarding the relative stability of H₂ O₂ andHOOAc in the concentrate composition and the concentrate itself areshown in FIGS. 1-14. Acetic acid typically was not measured forstability since it is not one of the active ingredients of theconcentrate composition; in other words, acetic acid has no microbicidalactivity. As can be seen from FIGS. 1-15, the solutions were verystable.

In addition to stability studies, corrosivity studies were run on theconcentrate compositions, the results of which may be seen by referringto Table IIA. Table IIB details the results of the corrosivity run onconventional art formulations while Table IIC details the results ofcorrosivity testing on the component parts of the conventional artformulation. Table IID details the results of corrosivity studies run onthe use-dilution formulations of the conventional art and several of thepreferred embodiments of the present invention.

Corrosivity studies were done using a variety of metal coupons. Theyincluded naval brass 464 and aluminum 5052. The coupons are commerciallyavailable from Metal Samples Company (Munford, Ala.)

Coupons were cleaned by the following methods to remove all foreigndebris and to ensure accurate results. Brass coupons were placed on edgein a 50% by weight solution of HCl for two minutes at ambienttemperature. Aluminum coupons were placed on edge in concentrated nitricacid for three minutes at ambient temperature. During all phases of thetesting, coupons were handled by gloved laboratory personnel to insurethat the coupons were not exposed to any foreign materials prior toplacing them in the test solutions. All coupons are stamped with anumber to aid in identification. All coupons were air dried under aventilated hood and weighed prior to testing on a Mettler AE 100analytical balance. The weight was recorded as the initial weight.

The exposure time of the coupons was 0.5 hours for brass and 5 hours foraluminum when testing the concentrate microbicide and 5 hours for brassand 1 week for aluminum when testing the use-dilution formulation of themicrobicide. The coupons were tested in the test solutions indicatedbelow at ambient temperature.

Solution volumes of 70 ml were dispensed into plastic disposable cups.The coupons were allowed to remain in solution for the times indicatedabove. After the time period had expired, the solution was discarded andthe coupons were plated to dry, without rinsing, standing on edge in aventilating hood. After drying for 30-60 minutes, the coupons werere-weighed. The difference between the initial weight and final weight(W) was used to calculated the corrosion rate as follows: ##EQU1##

K=a constant (8.76×10⁻⁴)

T=time of exposure in hours

A=area in cm⁻² (28.7 cm⁻²)

W=weight loss in grams (initial weight-final weight)*

*To correct for possible weight loss due to product removal, a "blank"coupon was weighed, cleaned by the procedure indicated above and weighedagain.

D=density in g/cm⁻³ **

**Brass=8.41 g/cm⁻³

Aluminum 5052=2.68 g/cm⁻³

                  TABLE IIA                                                       ______________________________________                                        Sam- Titrations        Corrosion                                              ples H.sub.2 O.sub.2                                                                        PAA     HoAc   Brass    Aluminum                                ______________________________________                                        1    38.8%    4.54%   2.88%   19.9 mm/yr                                                                            0.012 mm/yr                             2    34.8%    4.23%   3.27%   33.3 mm/yr                                                                             .006 mm/yr                             3    27.6%     5.0%    6.1%  52.02 mm/yr                                                                             .284 mm/yr                             4    27.4%     5.4%    6.2%  58.91 mm/yr                                                                             .024 mm/yr                             5    27.3%     5.5%    5.7%  52.07 mm/yr                                                                             .022 mm/yr                             6    27.55%   5.03%   6.06%  52.02 mm/yr                                                                             .283 mm/yr                             7    27.4%     5.4%   6.21%  58.91 mm/yr                                                                             .023 mm/yr                             8    27.34%   5.51%   5.68%  58.07 mm/yr                                                                             .020 mm/yr                             9    27.2%    5.72%   6.67%  57.56 mm/yr                                                                             .010 mm/yr                             10   27.2%    5.70%   6.82%  54.53 mm/yr                                                                             .376 mm/yr                             11   27.0%    5.62%   6.66%  49.96 mm/yr                                                                             .013 mm/yr                             12   27.0%    4.00%   5.71%  82.10 mm/yr                                                                             .001 mm/yr                             13   26.5%    4.14%   6.50%  93.70 mm/yr                                                                             .018 mm/yr                             14   22.5%    4.19%   7.84%  95.62 mm/yr                                                                            1.320 mm/yr                             15   22.5%    3.91%    8.1%  93.25 mm/yr                                                                             .153 mm/yr                             16   22.5%    3.86%    8.1%  93.20 mm/yr                                                                             .230 mm/yr                             17   19.6%    2.68%   8.62%   45.3 mm/yr                                                                             .257 mm/yr                             18   16.9%    1.66%   6.26%   43.4 mm/yr                                                                             .173 mm/yr                             ______________________________________                                    

                                      TABLE IIB                                   __________________________________________________________________________    Conventional Art Formulation                                                  Titration                                                                                      Phosphonic Acid                                                                        Corrosivity                                         Samples                                                                            H.sub.2 O.sub.2                                                                   PAA HoAc                                                                              Stabilizer                                                                             Brass  Aluminum                                     __________________________________________________________________________    19   22.4%                                                                             3.96%                                                                             8.27%                                                                             1.0%     295.50 mm/yr                                                                         121.63 mm/yr                                 20   21.0%                                                                             4.3%                                                                              9.86%                                                                             1.0%     295.48 mm/yr                                                                         121.65 mm/yr                                 __________________________________________________________________________

                  TABLE IIC                                                       ______________________________________                                        Corrosivity of Component Parts                                                Samples        Brass     Aluminum                                             ______________________________________                                        1% stabilizer  .586 mm/yr                                                                              .367 mm/yr                                           22.7% H.sub.2 O.sub.2                                                                        .528 mm/yr                                                                              .316 mm/yr                                           10.2% HoAc     .160 mm/yr                                                                              .167 mm/yr                                           ______________________________________                                    

                  TABLE IID                                                       ______________________________________                                        Use-dilution Formulations*                                                    Conventional Art                                                                              Brass      Aluminum                                           ______________________________________                                        3% Sample 19    23.63 mm/yr                                                                              0.820 mm/yr                                        3% Sample 20    23.84 mm/yr                                                                              0.747 mm/yr                                        Present invention                                                             Sample X [27% H.sub.2 O.sub.2,                                                                12.77 mm/yr                                                                              0.437 mm/yr                                        5.3% PAA, 5.5% Ac]                                                            Sample Y [37% H.sub.2 O.sub.2,                                                                 5.39 mm/yr                                                                              0.374 mm/yr                                        4.8% PAA, 2.2% Ac]                                                            Sample Z [22% H.sub.2 O.sub.2,                                                                14.63 mm/yr                                                                              0.441 mm/yr                                        4.0% PAA, 7.0% Ac]                                                            ______________________________________                                         *All usedilution samples were prepared using 3% of the concentrate formul     diluted in a purified aqueous diluent.                                   

In the present preferred form of the invention, the concentrate isshipped in a small quantity in an amber colored plastic bottle togetherwith a gallon of purified deionized water. Before use, the concentrateof the preferred embodiment is diluted from about 20 to 40 times, morepreferably from about 25 to 35 times, and most preferably from about 30to 33 times with a purified aqueous diluent prepared as described below.This results in a use-dilution formulation of approximately 3.0% to 4.5%by volume of concentrate. Ordinary tap water is generally unsuitable asa diluent because of contaminants, such as divalent and trivalent ions,contained therein. If ordinary tap water is used to dilute theconcentrate, the shelf life of the use-dilution formulation will likelybe less than when the purified aqueous diluent is used and corrosivitywill increase as the purity of the water decreases. The recommendedshelf life of the use-dilution microbicide is seven days. Consequently,it may be used for several applications or reused several times duringthat period of time with no change in the stability or in theanticorrosive or sporicidal activity.

A purified aqueous diluent suitable for use in the concentrate anduse-dilution formulation in accordance with the present invention isprepared in the following manner. Raw city water is passed through anactivated carbon bed containing 10 cubic feet of carbon in a 24 in.diameter fiberglass tank with a 2 in. diameter super flow head and a 2in. diameter distributor.

The water is then passed through softening beds well known in the art ofwater purification to remove calcium chloride and magnesium. Suitablesoftening beds are available from Eco water Systems (Woodbury, Minn.).The water is then passed through a one micron polypropylene clothsediment filter having an efficiency rate of 93%. The cloth filtercatches any particulate matter remaining in the water that has a sizegreater than 1_(u).

The water then flows through an eight inch diameter reverse osmosismembrane filter. The membrane filter is made from a spirally woundpolyamide sheet membrane and is commercially available as Model No.BW-30 from Filmtec Co. (Edina, Minn.). The water effluent has less than5 ppm dissolved solids.

After the water is treated by passing it through the reverse osmosismembrane, it is circulated through an ultraviolet disinfection unit. Theunit employs dual wave lengths at 185 nm and 254 nm and is rated at99%.9 bacterial reduction. A suitable commercially available unit is theAquafine U.V. Water Sterilizer, CLS-4R (Aquafine Corp, Valencia, Calif.)

Post-UV light treatment, the water flows through an anion exchange resinbed and a cation exchange resin bed. The anion exchange resin bed is astrongly basic anion exchange resin based on a styrenedivinylbenzenecopolymer matrix. Its exchange capacity is derived from the N·(CH₃)₂ H₄OH (dimethylethanolamine) group. Anion exchange resin bed capable ofpurifying the aqueous diluent in accordance with the present inventionmay be purchased from Sybron Chemicals Inc (Birmingham, N.J.) under thetrade name IONAC ASB-2. The cation exchange resin bed is a bead-form,standard crosslinked, polystyrene sulfonate cation exchange resin with acapacity of 1.4 mEq/ml for further demineralization. Treated water isstored in a 1000-5000 gallon tank. Resistivity is constantly measuredand maintained at 17-17.5 mOhms.

Prior to using the above manufactured water in the concentrate mixturesor use-dilution formulations in accordance with the present invention,the water is tested for pyrogen, yeast, molds and bacteria by thefollowing methods.

Pyrogen Testing. Five milliliters of sterile water is pipetted into avials of endotoxin, commercially available as endotoxin from E. colistrain 055.B5 from Whittaker Bioproducts, Inc. (Walkersville, Md.). Fiveand two-tenths milliliters of sterile water is piperted into a vial oflysate, commercially available as Pyrogen T from Whittaker Bioproducts.One hundred lambda of the reconstituted lysate is then piperted intodisposable conical tubes. The diluted lysate has a sensitivity of 0.06endotoxin units.

Serial dilutions of the reconstituted endotoxin ranging from 500picograms/ml to 12.5 picograms/ml are prepared. Positive controls areset up by pipetting 100 lambda of each of the above prepared dilutionsof endotoxin into a conical tube containing the lysate. Tubes are mixedand placed in a 37° heating block for one hour±two minutes. Triplicatesamples of 100 lambda each of ultra-pure deionized water as manufacturedin accordance with the procedure disclosed herein are added to thelysate tubes and incubated at 37° C. for one hour. A gelled tubeindicates the presence of endotoxin.

Yeast, Molds and Bacteria Testing

Water used in the manufacture of the concentrate microbicide and in theuse-dilution formulation is tested for the presence of microbes using afilter membrane technique. Samples are collected aseptically in sterile10 ml test tubes at the source. Five milliliters of sample is transferedinto a 100 ml filter housing. A vacuum is applied to the filter housingto facilitate filtration. The lower housing is removed and the filtrateis decanted. The filter membrane is aseptically removed and placed in atryprone glucose yeast agar plate (DiMed Corporation, St. Paul, Minn.)for measuring bacterial growth and potato dextrose agar plates (DiMedCorporation, St. Paul, Minn.) for measuring yeast and mold growth. Themedia plate is covered, inverted and incubated at 35° C. for two daysfor bacteria and at 22° C. for seven days for yeasts and molds. Resultsare reported as the number of colony forming units per five millilitersof sample size.

EXAMPLES Example 1

All mixing drums and tanks were thoroughly cleaned using purified water.Sixty percent by weight of purified water was added to a cleaned mixingtank at ambient temperature. Bacterial testing and yeast and moldstesting of the water used in manufacturing the concentrate was reportedas 0 colony forming units per five milliliters of sample for both tests.An air driven drum pump was turned on to start recirculation of thebatch. Fourteen percent by weight of acetic acid was added to the mixingtank containing the deionized water. After the acetic acid was added,the batch was covered and recirculated for one hour. Using an air drivendrum pump, 26% by weight of hydrogen peroxide was added into the mixingtank and the cover replaced. The composition was recirculated for twohours after all chemicals were added. After two hours, the recirculatingpump was stopped. The concentrate was dispensed into clean 55 gallondrums for storage and equilibrated for 19 days. After 19 days from theproduction date, a sample was taken from the concentrate batch and theconcentration was determined to be 22.5% H₂ O₂, 3.96% peracetic acid,and 8.1% acetic acid.

Microbicidal Effectiveness

A 3.0% solution of the concentrate microbicide manufacture in Example 1was tested for sporicidal activity according to the methods outlined inthe Official Methods of Analysis of the Association of OfficialAnalytical Chemists (K. Helrich 15th ed. 1990) (966.04 pp. 141-142), thetext of which is hereby specifically incorporated by reference.

Briefly, cultures of two sporoformer organisms, Bacillus subtilis ATCC19659 and Clostridium sporogenes ATCC 3584 were grown in the appropriatemedium. Each organism was used to contaminate two types of carriers,namely, silk suture and porcelain penicylinders. The carriers were driedfor a minimum of 24 hrs. under vacuum. Carriers were tested for acidresistance and viability. Five carriers were placed in test tubescontaining 10 mL. of test solution, and exposed for 30 min. at 50° C.Following contact, carriers were neutralized in thioglycollate mediumand incubated for 21 days at 37° C. If no growth was observed after 21days, the test tubes were heat shocked for 20 minutes at 80° C. toactivate any remaining spores and incubated for 72 hrs. at 37° C. Forchemical sterilant claims, no survival of any organism/spore can betolerated for qualification of the solution by the U.S. EnvironmentalProtection Agency as a sterilant. The results of the sporicidal testingof the concentrate microbicide in accordance with the microbicideprepared in Example 1 are as follows:

    ______________________________________                                                                           #Survivors/                                Lot    Org. Carrier Titer  Resistance                                                                            #Tested                                    ______________________________________                                        2M004  Cl. sp. Suture                                                                             10.sup.- 6                                                                           20 min. 0/60                                       2M004  Cl. sp. Cylinder                                                                           10.sup.- 5                                                                            5 min. 0/60                                       2M004  B. sub. suture                                                                             10.sup.- 4                                                                           20 min. 0/60                                       2M004  B. sub. Cylinder                                                                           10.sup.- 4                                                                            2 min. 0/60                                       ______________________________________                                    

The results of the AOAC procedure reference test shows that themicrobicide of the invention, in addition to being stable, is effectiveas a sterilant.

Corrosivity of the solution of Example 1 was tested. The results appearas Sample 15 in Table IIA.

Example 2

All mixing drums and tanks were thoroughly cleaned using purified water.23.3% by weight of purified water was added to a cleaned mixing tank atambient temperature. Bacterial testing and yeast and molds testing ofthe water used in manufacturing the concentrate was reported as 0 colonyforming units per five milliliters of sample for both tests. An airdriven drum pump was turned on to start recirculation of the batch.16.7% by weight of acetic acid was added to the mixing tank containingthe purified water. After the acetic acid was added, the batch wascovered and recirculated for one hour. Using an air driven drum pump,40.0% by weight of hydrogen peroxide was added into the mixing tank andthe cover replaced. The composition was recirculated for two hours afterall chemicals were added. After two hours, the recirculating pump wasstopped. The concentrate was dispensed into clean 55 gallon drums forstorage. After 19 days from the production date, the batch was adjustedto a hydrogen peroxide level of 36.5% and a peracetic acid level of 4.5%by adding water and hydrogen peroxide. The solution was allowed toequilibrate for an additional 33 days. A sample was taken from theconcentrate batch and the concentration was determined to be 36.65%hydrogen peroxide, 4.31% peracetic acid and 2.88%.

The results of the sporicidal testing of a 3% solution of theconcentrate microbicide in accordance with the microbicide prepared inExample 2 are as follows:

    ______________________________________                                                                           #Survivors/                                Lot    Org. Carrier Titer  Resistance                                                                            #Tested                                    ______________________________________                                        2008-2a                                                                              Cl. sp. Suture                                                                             10.sup.- 6                                                                           20 min. 0/60                                       2008-2a                                                                              Cl. sp. Cylinder                                                                           10.sup.- 6                                                                           10 min. 0/60                                       2008-2a                                                                              B. sub. suture                                                                             10.sup.- 4                                                                           10 min. 0/60                                       2008-2a                                                                              B. sub. Cylinder                                                                           10.sup.- 4                                                                            2 min. 0/60                                       ______________________________________                                    

The concentrate prepared in accordance with Example 2 was tested forcorrosivity. The results are shown in Table IIA as Sample 2.

Example 3

Using the method set forth in Examples 1 and 2, 7.74% by weight purifiedwater was added to 17.12% by weight H₂ O₂ and 8.143% by weight HOAc.Bacterial testing and yeast and molds testing of the water used inmanufacturing the concentrate was reported as 0 colony forming units perfive milliliters of sample for both tests. After mixing for thespecified time periods, the concentrate was allowed to stand for 19 daysand a sample was taken to determine the content of H₂ O₂ and HOOAc. Thefinal concentration was determined to be 16.86% by weight H₂ O₂, 1.66%peracetic acid and 6.26% acetic. The solution was found to havemicrobicidal activity as follows:

    ______________________________________                                                                           #Survivors/                                Lot    Org. Carrier Titer  Resistance                                                                            #Tested                                    ______________________________________                                        2028-1 Cl. sp. Suture                                                                             10.sup.- 5                                                                           10 min. 0/60                                       2028-1 Cl. sp. Cylinder                                                                           10.sup.- 6                                                                           10 min. 0/60                                       2028-1 B. sub. suture                                                                             10.sup.- 4                                                                           10 min. 0/60                                       2028-1 B. sub. Cylinder                                                                           10.sup.- 4                                                                            2 min. 0/60                                       ______________________________________                                    

Corrosivity was tested and the results are detailed in Table IIA asSample 18.

While the preceding compositions in accordance with the invention arethe preferred form it is to be understood that concentrate formulationsmay be within the ranges given and still provide the advantages of theinvention. Those skilled in the art may recognize other equivalents tothe specific embodiments described herein which equivalents are intendedto be encompassed by the appended claims.

We claim:
 1. A stable, anticorrosive to surgical and dental metalsconcentrate consisting essentially of at equilibrium peracetic acid,acetic acid, hydrogen peroxide and an aqueous diluent, said concentratecharacterized in having from about 0.001-200 ppm of stabilizers whereinsaid stabilizers are selected from the group consisting of phosphonicacids and sodium pyrophosphates, from about 5-10 ppm of divalent andtrivalent ions wherein said divalent and trivalent ions are selectedfrom the group consisting of iron, manganese, magnesium, nickel andcobalt and no added surfactants.
 2. The concentrate in accordance withclaim 1 wherein the concentration of said stabilizers are from about0.001-100 ppm.
 3. The concentrate is accordance with claim 1 wherein theconcentration of said stabilizers is from about 0.001-10 ppm.
 4. Theconcentrate of claim 1 wherein the equilibrium composition comprises:

    ______________________________________                                        a)       H.sub.2 O.sub.2                                                                        16 to 38% by weight;                                        b)       HOAc     2.0 to 9.0% by weight;                                      c)       HOOAc    1.5 to 6.0% by weight; and                                  d)       the balance is a purified aqueous diluent.                           ______________________________________                                    


5. The concentrate in accordance with claim 4 wherein the concentrationof said stabilizers is from about 0.001-100 ppm.
 6. The concentrate inaccordance with claim 4 wherein the concentration of said stabilizers isfrom about 0.001-10 ppm.
 7. The concentrate in accordance with claim 1wherein the equilibrium concentration comprises:

    ______________________________________                                        a)      H.sub.2 O.sub.2                                                                           23 to 24% by weight;                                      b)      HOAc         9 to 10% by weight;                                      c)      HOOAc        4 to 6% by weight; and                                   d)      the balance is a purified aqueous diluent.                            ______________________________________                                    


8. The concentrate in accordance with claim 7 wherein the concentrationof said stabilizers is from about 0.001-100 ppm.
 9. The concentrate inaccordance with claim 7 wherein the concentration of said stabilizers isfrom about 0.001-10 ppm.
 10. A method of formulating a stable,anticorrosive to surgical and dental metals concentrate microbicidecomprising the steps of:a) blending hydrogen peroxide, acetic acid and apurified aqueous diluent to result in a solution which at equilibriumhas from about 0.001-200 ppm stabilizers wherein said stabilizers areselected from the group consisting of phosphonic acids and sodiumpyrophosphates, from about 5-10 ppm of divalent and trivalent ionswherein said divalent and trivalent ions are selected from the groupconsisting of iron, manganese, magnesium and cobalt and no addedsurfactants.
 11. A method of formulating a stable, anticorrosive tosurgical and dental metals concentrate microbicide comprising the stepsof:a) introducing from about 17% by weight to about 40% by weighthydrogen peroxide into a mixing drum, said hydrogen peroxide ischaracterized in having from about 0.001-200 ppm of stabilizers whereinsaid stabilizers are selected from the group consisting of phosphonicacids and sodium pyrophosphates; b) blending thereinto from about 10% byweight to about 16% by weight acetic acid; and c) adding a purifiedaqueous diluent having from about 5-10 ppm of divalent and trivalentions wherein said divalent and trivalent ions are selected from thegroup consisting of iron, manganese, magnesium, nickel andcobalt;wherein the equilibrium concentration comprises: i) from about16-34% by weight hydrogen peroxide; ii) from about 5-12% by weightacetic acid; iii) from about 2.5-5.5% by weight peracetic acid; and iv)an aqueous diluentand wherein said equilibrium concentrate ischaracterized in having from about 0.001-200 ppm of stabilizers whereinsaid stabilizers are selected from the group consisting of phosphonicacids and sodium pyrophosphates, from about 5-10 ppm of divalent andtrivalent ions wherein said divalent and trivalent ions are selectedfrom the group consisting of iron, manganese, magnesium, nickel andcobalt and no added surfactants.
 12. A stable, anticorrosive to surgicaland dental metals use-dilution microbicide comprising:a) a concentrateconsisting essentially of at equilibrium peracetic acid, acetic acid,hydrogen peroxide and an aqueous diluent, said concentrate characterizedin having from about 0.001-200 ppm of stabilizers wherein saidstabilizers are selected from the group consisting of phosphonic acidsand sodium pyrophosphates, from about 5-10 ppm of divalent and trivalentions wherein said divalent and trivalent ions are selected from thegroup consisting of iron, manganese, magnesium, nickel an cobalt and noadded surfactants; and b) a purified aqueous diluent;wherein saidconcentrate is diluted in said aqueous diluent from about 20 to 40times.